Gaseous discharge tube



June 29, 1954 A H B, SLOAN 2,682,621

GASEOUS DISCHARGE TUBE Filed Deo. 3l, 1948 i, `I" (wf i FHM $1 l @il i 3 2H ki/ M' il 7 INVENTOR.

ATTORNEY.

Patented June 29, ,1954

UNITED STATES PATENT OFFICE GASEOUS DISCHARGE TUBE Howard B. Sloan, Lynn, Mass., assignor to Sylvania Electric Products Inc., Salem, Mass., a corporation of Massachusetts Application December s1, 194s, serial No. 68,623

2 Claims. 1

This invention relates to electric gaseous discharge tubes in general and in particular to such devices having a cathode comprising a highly electron-emissive material.

Ilhe invention is especially directed to discharge tubes of this type for pulsed excitation.

An object of the invention is to prolong the life of such tubes and particularly to their cathodes.

Further objects are to reduce sputtering from the cathode and the consequent blackening of the tube walls.

A feature of the invention is an insulating tube around the cathode. Another feature is an enlarged electrode chamber in the neighborhood of said cathode and a further feature is an insulating tube extending into said chamber toward said cathode and spaced from the iirs't-*nentione insulating tube.

Other features, objects and advantages of the invention will be apparent from the following specification taken in connection Iwith the accompanying drawings, in which:

Fig. 1 represents a prole view, partly cut away, of a tube according to the invention; and

Fig. 2 is a view, partly in section, of a cathode chamber according to a variation of the invention.

In Figure 1 the tubular glass envelope I has the anode Wire 2, preferably of tantalum, sealed through one end. The enlarged electrode chamber 3 is sealed to the other end and the lead-in wire ffl lsealed through the end of said chamber 3. The tantalum cathode strips 5 constituting a cold type of cathode, lacking a heater, is welded or otherwise attached to diametrioally opposite parts of the lead-in wire 4 near the inner ends thereof. These strips may be bent toward each other above the inner end 3 of lead-in wire e and may be welded cr otherwise fastened together where they meet, for example at the intermediate portions 9, and be afterward flared outward from each other at their free ends 5 and 'I. The flared free ends S, l, may be coated, for example, with a mixture of barium, strontium and calcium carbonates or nitrates, common in the art, preferably with the addition of a small amount of nickel nitrate. This cathode structure 5 may be enclosed in a glass tube or inert sleeve lil concentric therewith and ending near the free end of the cathode 5. Another glass tube H preferably of slightly larger diameter extends into the electrode chamber 3 from the tube I toward the cathode 5 and terminates a short distance away from the tube I0 which therefore does not open rfreely into chamber 3 but, instead, tube Il) ycommunicates with chamber 3 through a constricted 2 passage. The tube may be coiled to have several turns I2, I3, if desired. The tube may be lled with an inert gas, for example xenon at a pressure which may -be for example, 75 mm. of mercury.

In Fig. 1, the tube II is spaced longitudinally from tube IE). Figure 2 shows an arrangement Where tube I I extends beyond the end of tubel0, but is spaced radially therefrom.

In operation the lead-in wires 4 and M may be connected across a suitable source of voltage, generally of a highly pulsed type, for example, across a condenser. If desired,'a starting wire I5 may be Wrappedaround suitable portions of the tube I, as shown for example in copending application Serial No. 18,254 led March 31, 1948, by Harold Heins and Donald Coggins. This device is very suitable for airport approach lighting systems such as that there shown. The use of the insulating tubes l0 and Il has been found to greatly increase the life of tubes of this nature and at the same time to make a tremendous decrease in the blackening of the tube particularly in the neighborhood of the cathode 5. Apparently this is due to the building up of a pressure in tube I during the discharge, this pressure forcing gas out into the main electrode chamber 3 through the constricted space between the ends of tubes IU and I I, the pressure in electrode chamber 3 remaining low. However I do not Wish to be bound by this theory for the mechanism of my invention is still somewhat obscure,

although the results obtained are quite denite. The tubes l0 and I l may be used with other types of cathode without departing from the spirit of the invention and I have found the type of cathode described to be especially useful.

Other transparent insulating materials for example quartz may be used instead of glass in a device according to my invention; the word glass being used in my specication and claims in a generic sense to include such materials.

What I clamvis:

1. An electric discharge lamp comprising an enclosing envelope having a coiled light-emitting portion and containing a gas, an anode at one end thereof, and a cathode at the other, said envelope having an enlarged chamberat the end near the cathode, a reentrant tube extending and communicating from the light-emitting portion into said chamber toward said cathode, and another tube open toward but spaced from said reentrant tube and enclosing said cathode except for this opening.

2. An electric vdischarge lamp lcomprising an enclosing envelope having a coiled light-emitting portion and containing a gas, an anode at one end thereof, and a Cathode at the other, said envelope having an enlarged chamber at the end near the cathode, a reentrant tube extending and communicating from the light-emitting portion into said `chamber toward said cathode, and another tube spaced longitudinally from said reentrant tube and otherwise Isurrounding said cathode but spaced therefrom.

References Cited in the file of this patent 2 UNITED STATES PATENTS Number Name Date 1,173,542 Skaupy Apr. 11, 1916 1,856,758 Goddard May 3, 1932 1,858,298 Zons May 17, 1932 Number Name Date Found Nov. 14,1933 Wiegand Aug. 28, 1934 Ryde May 28, 1935 Nauth Oct. 20, 1936 Pirani July 20, 1937 Gooskens May 3, 1938 Germer July 25, 1939 Spanner Jan, 14, 1941 FOREIGN PATENTS Country Date Great Britain Sept. 6, 1940 Germany May 23, 1921 Germany May 10, 1935 IAustralia Jan. 12, 1939 Italy Nov. 24, 1931 

